Compact lithium ion battery and method of manufacturing

ABSTRACT

Described is a lithium ion battery  10  comprising:  
     A housing having a front side  13  and a backside  15  and an anode cell terminal  60  and a cathode cell  44  terminal separated therefrom;  
     Positioned within the housing a plurality of bipolar lithium ion cells  40  having an lithium ion permeable plastic separator  32  there between; the cell electrodes being comprised of a thin film plastic substrate  34  and being electrically connected appropriately to the anode and the cathode cell terminals;  
     wherein the cells are longitudinally placed in the housing parallel to the sides of the housing; and  
     wherein the housing is enclosed by the cathode cell terminal at one end and the anode cell terminal at the opposite end of the cell sleeve; and  
     the enclosed housing is capable of receiving an electrolyte placed between the cells and the electrolyte is capable of carrying ions between the anode and the cathode  
     Also described is a method of manufacturing the lithium ion batteries.

FIELD OF THE INVENTION

[0001] The present application pertains to rechargeable lithium ionbatteries, and in particular, to a compact lithium ion battery moduleutilizing bipolar electrodes.

BACKGROUND OF THE INVENTION

[0002] Lithium batteries are seen by many to be an attractive energystorage device. Lithium ion batteries have been targeted for variousapplications such as portable electronics, cellular phones, power tools,electric vehicles, and load-leveling/peak-shaving. The batteries arecurrently replacing many other traditional power sources such as leadacid batteries, nickel cadmium batteries, and nickel metal hydridebatteries. Lithium ion batteries have been known to be out for manyyears (see the Handbook of Batteries, David Linden, editor, secondedition by McGraw-Hill, copyright 1995, in particular, chapters 36 and39). Various aspects of lithium batteries have been described in avariety of U.S. Patents, such as U.S. Pat. No. 5,961,672 pertaining to astabilized anode for lithium polymer batteries. U.S. Pat. No. 5,952,126pertains to polymer solid electrolyte and lithium secondary cells. U.S.Pat. No. 5,900,183 pertains to polymer electrolytes as well as does U.S.Pat. No. 5,874,185. U.S. Pat. No. 5,849,434 describes non-aqueouselectrolyte lithium secondary batteries. Other variations on lithiumbatteries are described in U.S. Pat. Nos. 5,853,914 and 5,773,959.

[0003] Appropriately packaging lithium ion batteries is particularlydifficult in the automotive environment due to the need for corrosionresistance, crush and crash worthiness, and vibration resistance. Theproblems of such batteries can be characterized as a need for betterseal robustness, namely overcome leak potential from internal pressure;better packaging robustness, namely better crush/crash worthiness;better thermal exchange properties, namely ability to dissipate heat andreceive cooling more effectively; ease of processing and transitioninginto mass production, that is, processes that lend themselves toautomation.

[0004] It is an object of the present invention to provide a lithium ionbattery wherein bipolar electrodes are utilized with a lithium ionpermeable polymer membrane or separator there between, and the cellelectrodes being electrically connected appropriately to the anode andcathode terminals which are at opposite ends of the housing for thebattery.

SUMMARY OF THE INVENTION

[0005] Described is a lithium ion battery 10 comprising:

[0006] A housing 12 having a front side 13 and a backside 15 and ananode terminal 60 and a cathode terminal 44 separated therefrom;

[0007] positioned within the housing a plurality of bipolar lithium ioncells 40 having a polymer separator 32 there between, optionally alithium ion permeable membrane; the cell electrodes being comprised of athin film plastic substrate 34 and being electrically connectedappropriately to the anode and the cathode terminals, respectively;

[0008] wherein the cells are longitudinally placed in the housingparallel to the sides of the housing; and

[0009] wherein the housing is enclosed by the cathode terminal at oneend and the anode terminal at the opposite end of the housing; and

[0010] the enclosed housing is capable of receiving an electrolyteplaced between the cells and the electrolyte is capable of carrying ionsbetween the anode and the cathode.

BRIEF DESCRIPTION OF THE DRAWINGS

[0011]FIG. 1 is an exploded view of the compact lithium battery which iscomprised of a cell sleeve and plastic end sleeves of the presentinvention.

[0012]FIG. 2B is a side sectional view of FIG. 2A.

[0013]FIG. 3 is an exploded view of the bipolar electrodes with anon-permeable or permeable separator there between as utilized in thepresent invention.

[0014]FIG. 4 depicts the bipolar stack of electrodes attached to thecathode cell terminal with the cathode grid ultrasonically weldedthereto.

[0015]FIG. 5 is a perspective view of the lithium ion battery of thepresent invention with the battery stack welded on the cathode end andinserted into the cell sleeve.

[0016]FIG. 6 is a top sectional view of FIG. 5.

[0017]FIG. 7 depicts the first step in attaching the anode cell terminalto the anode grid of the bipolar electrodes and is a top sectional viewof FIG. 5, anode side.

[0018]FIG. 8 shows the anode terminal secured to the anode grid of thebipolar electrode stack.

[0019]FIG. 9 depicts the lithium ion battery of the present invention inits final form, prior to crimping and securing the battery housingcomprised of a cell sleeve within the end terminals.

[0020]FIG. 10 is a top sectional view of the battery of FIG. 9.

[0021]FIG. 11 depicts the top partial sectional view of the cell housingshowing the first step of the crimping of the end terminals to thehousing.

[0022]FIG. 12 is the second step in the crimping of the battery cellterminals to the housing.

[0023]FIG. 13 is the third step in the crimping of the battery cellterminals to the housing

[0024]FIG. 14 is the final step in the crimping process of securing thebattery cell terminals to the housing.

[0025]FIG. 15 is a finished lithium ion battery being covered with aprotective wrap.

[0026]FIG. 16 is the backside view of FIG. 15.

DESCRIPTION OF PREFERRED EMBODIMENTS

[0027] The present invention pertains to lithium ion batteries that areprepared into compact, bipolar cell arrangements. While bipolar cellsare demonstrated in the present invention, monopolar cells may likewisebe utilized. A wide variety of rechargeable lithium batteries may beutilized, such as those disclosed in Chapter 36 in the Handbook ofBatteries, supra, U.S. Pat. No. 5,460,904 and U.S. Pat. No. 5,456,000.

[0028] Turning now to the drawings, FIG. 1 depicts the lithium ionbattery 10 with its component parts, namely, the housing or cell sleeve12 which has end protective plastic sleeves 14 and 16 with extensions 17for the anode side and 22 for the cathode side which fit within the cellsleeve interior 20 to secure and isolate the bipolar cells therein. Thecell sleeve 12 has an end 21 near the anode terminal 60 and an end 23near cathode terminal 44. The use of the terminology “sleeve” isappropriate for the housing. It connotes a rectangular open structure inwhich the battery stack is placed.

[0029] A one-way valve housing 18 is pressed and soldered into the anodecell terminal 60 and has an extended portion 24 which fits within theinterior 20 of the cell sleeve. The valve housing 18 has a valve thatfits in the interior of the cell, which permits a gas to be releasedtherefrom. In addition, during the manufacturing and assembling of thecell, electrolyte may be passed through the port 26 of the anodeterminal 60.

[0030] The electrode stack 40 is comprised of bipolar electrodes 36 withlithium ion permeable polymer membrane 32 between the different cells.Optionally the membrane 32 is not lithium permeable. While a widevariety of materials can be utilized for the bipolar cells and thepolymer membrane, one type of cathode could be a lithium metal oxidesuch as lithium manganese oxide or lithium cobalt oxide. The anode maybe a carbon plastic film with a copper current collector. The bipolarelectrodes utilize a stable substrate 34 on which is deposited a lithiumion material 36. The substrate for the lithium cathode can be a materialthat is stable in the environment of lithium ion cells having athickness of less than 100 mils. A wide variety of thin film plasticsubstrates may be utilized, such as polyvinylidene difluoride (PVDF).The polymer membrane or separators 32 likewise can be a wide variety ofthin film plastic materials having a thickness of less than 100 mils.One material is Mylar (trademark of DuPont for a polyester film).

[0031] As shown in FIG. 3, the bipolar stack of electrodes 40 isattached to the cathode cell terminal 44 which has a lip thereto 46. Thecathode cell terminal has an extension 48 which surrounds the cellsleeve 23 (see FIG. 10). The cathodes are secured to one anotherultrasonically and also to the cathode terminal 44 by means of theextended grid 64.

[0032]FIGS. 4, 5 and 6 depict the ultrasonic weld attaching theextension 64 to the interior portion 72 of the cathode 44. Commerciallyavailable ultrasonic welding equipment may be utilized such as CondorST301 (trademark of Stapla Corp.)

[0033] The anode terminal 60 has an anode grid strip 62 mechanicallysecuring each of the anode grids together. They are ultrasonicallywelded together by the commercially available equipment. See FIGS. 5 and7.

[0034]FIG. 7 depicts the anodes ultrasonically welded to the extension62. The lip of the cell sleeve 21 is shown as captured within theinterior 72 of the anode. The anode 60 has a lip portion 70 withextension portions 75 which snugly cover cell sleeve 21 (see FIGS. 7 and10).

[0035] After the cathodes of the bipolar electrode stack 40 areultrasonically welded to the cathode terminal 44, the cell sleeve 12 maybe slid over the stack. Then the cathode cell terminal 44 may be pivotedas shown in FIG. 5 onto the end 23 of the cell sleeve. The anodes of thebipolar stack, as shown in FIGS. 5 and 7, may be then ultrasonicallywelded to the anode cell terminal 60. The anode cell terminal 60 has alip portion 70 as best shown in FIGS. 5 and 7. The anode cell terminal60 may then be pivoted onto the end of the cell sleeve 21 as shown inFIG. 8. The lithium ion battery takes on the appearance of a cell can asshown in FIG. 10. It is then ready for crimping to secure the bipolarstack within the sleeve as shown in FIGS. 9 and 10. The cell terminalsare crimped about the cell sleeve in four stages as shown schematicallyin FIGS. 11, 12, 13, and 14. Only the cathode end is depicted in FIGS.11-14. Clearly the same is applicable on the anode side as well. Theplastic sleeve 16 is depicted in FIGS. 11-14, and its extension 22 fitssnugly within the cell sleeve 12. As can be seen in FIGS. 11-14, thesleeve extension 22 electrically insulates the cathode 44 from the cellhousing 12.

[0036] To further insulate the battery components, the lithium ionbattery may be wrapped with a cell wrap 84 which is a plastic materialas polyethylene or polypropylene as shown in FIGS. 15 and 16. A seal 86is present on the sleeve to electrolytically insulate the sleeve fromthe battery stack 40. The extensions 22 for the cathode plastic insertand 17 for the anode plastic insert fit within the interior 20 of thesleeve 12. The extensions are generally made of a stable plasticmaterial, namely one that is stable within the environment of thelithium ion batteries. It is comprised of a material that is resistantto electrolyte such as a polypropylene and the like.

[0037] The cathode materials are comprised of the same polymer as theelectrodes. They may or may not comprise stabilizing materials such assilica or plasticizer. The plasticizer, during the manufacturingprocess, will be dissipated and is generally not present in the finalproduct.

[0038] The present invention provided for ganging the electrode gridswhich are present in the flat stack and ultrasonically welding the gridstack to the inside of each appropriate stack end, namely the cellterminal. Thereafter, the crimping may permit sealing the sleeve shut.

[0039] Further, a plastic sleeve is contained in each crimp and acts asa seal and electrical insulator between the sleeve parts and between thegrid and sleeve parts.

[0040] The valve housing serves multiple purposes. The housing initiallyprovides a port for activation by filling electrolyte therein. Then itprovides for the containment of the valve and permits release of gas.

[0041] The large metallic surfaces 12 act as a good thermal insulator,that is metallic surfaces of the housing.

[0042] By virtue of the crimping process, a good seal is obtainedbecause malleable plastic components create a robust package, that is apackage that is crush/crash worthy.

[0043] By virtue of the ultrasonic welding of the electrodes to therespective anode terminal and cathode terminal, there is good currentdistribution across the active materials and out to the cell terminals.

[0044] It is to be appreciated that the number of electrodes in thebattery stack can vary. One configuration has about 45 bicellscontaining 9 anodes and 45 cathodes having a capacity of 30-40 amp hoursat about 4 volts.

[0045] It is understood that the following claims are intended to coverall of the generic and specific features of the invention hereindescribed. And all statements of the scope of the invention which as amatter of language might be said to fall there between.

[0046] While the forms of the invention herein disclosed constitutepresently preferred embodiments, many others are possible. It is notintended herein to mention all of the possible equivalent forms orramifications of the invention; it is understood that the terms usedherein are merely descriptive rather than limiting and that variouschanges may be made without departing from the spirit or scope of theinvention.

1. A lithium ion battery comprising: A housing having a front side and abackside and an anode terminal and a cathode terminal separatedtherefrom; Positioned within the housing a plurality of bipolar lithiumion cells having a polymer separator there between; the cell electrodesbeing comprised of a thin film plastic substrate and being electricallyconnected appropriately to the anode and the cathode cell terminals;wherein the cells are longitudinally placed in the housing parallel tothe sides of the housing; and wherein the housing is enclosed by thecathode cell terminal at one end and the anode cell terminal at theopposite end of the housing; and the enclosed housing is capable ofreceiving an electrolyte placed between the cells and the electrolyte iscapable of carrying ions between the anode and the cathode:
 2. Thebattery of claim 1 wherein the housing is in the configuration of a openrectangular sleeve into which the cells fit.
 3. The battery of claim 1wherein the one of the terminals has a port for insertion of electrolyteinto the battery after assembly of the cells within the housing.
 4. Thebattery of claim 1 wherein one of the terminals has a vent for gasrelease therefrom.
 5. The battery of claim 1 wherein the cells areretained within a cell sleeve surrounding the longitudinal length of thecells within the housing.
 6. The battery of claim 5 wherein the cellsleeve extends beyond the length of the cells and which extensions areretained in a plurality of metallic clips, one of which is the anode andanother is the cathode.
 7. A method of manufacturing a lithium ionbattery comprising: Providing a plurality of bipolar lithium cells witha polymer separator there between; Electrically attaching the anodes ofthe cells to an anode terminal and the cathodes of the cells to acathode terminal; Positioning the cells longitudinally within a housinghaving a front and a backside thereto so as to be parallel to the sidesof the housing; and Assembling the anode cell terminal at one end of thehousing and the cathode cell terminal at the opposite end of the housingthereby enclosing the cells within the housing.
 8. The method of claim 6wherein the anodes are ultrasonically welded to the anode cell terminaland the cathodes are ultrasonically welded to the cathode cell terminal.9. The method of claim 6 wherein the anode and cathode terminals arecrimped to the housing, thereby providing a seal of the cell terminalsto the housing.
 10. The method of claim 6 further comprising inserting agas release vent into a port in the one-way valve housing attached tothe anode cell terminal.
 11. The method of claim 1 wherein the housingis in the configuration of an open rectangular sleeve prior topositioning the cells therein.